You run a task to completion, then upload & report it. Then you wait for a wingman to do the same. When that's done, the server will validate the result files, see if their outcome is approximately the same. When that's done, credit is granted and this task value is stored in the BOINC database and shown for the computer IDs that did the task. The outcome of the result file is stored in the science database.

After a certain period of time, the task value is deleted from the database. This is done to make room for more outcomes.

There is no physical way for the project to show all the task IDs and their credit for everyone who is doing this project for all the years that they've done this project for all the computers that have crunched every piece of data. The database would be astronomically big. And it's not needed anyway, as the result file (the actual science) is stored in the science database, and you and your wingman have been paid in credits.

You won't lose credit when the tasks are removed from the database. What you've been paid for will stay with you. Unless, of course, you restart and register with a new account every time. Which is what you appear to have been doing.
____________Jord